1. Field of the Invention
This invention relates to a device for locking a seat post relative to a seat tube of a bicycle frame, more particularly to a locking device for releasably locking the seat post on the seat tube.
2. Description of the Related Art
A conventional locking device for locking a seat post on a seat tube of a bicycle frame includes a flexible tubular member which can be wrapped tightly around the seat post and which can be inserted into the seat tube. The seat tube has a slit which extends downwardly from an upper surrounding edge thereof. A C-shaped clamp ring is wrapped around the seat tube, and includes two jaw portions which are spaced apart from each other and which have through holes such that a quick-release fastener can pass through the through holes to engage a screw nut at one end thereof, and to be turnable at an opposite end thereof to bring the jaw portions towards each other so as to narrow the slit, thereby tightening the position of the flexible tubular member relative to the seat tube. However, the position of the flexible tubular member relative to the seat tube is not sufficiently firm. In addition, friction between the flexible tubular member and the seat tube remains even when the quick-release fastener is released, thereby resulting in inconvenience during height adjustment of the seat post relative to the seat tube.
The object of the present invention is to provide a locking device which can tighten firmly a seat post relative to a seat tube of a bicycle frame, and which permits a convenient height adjustment of the seat post relative to the seat tube.
According to this invention, the locking device includes a tubular body which has a lower surrounding member adapted to be secured to a seat tube of a bicycle frame, and an upper surrounding member extending upwardly in an axial direction from the lower surrounding member to terminate at an upper surrounding edge. The upper surrounding member has an outer surrounding wall surface, an inner surrounding wall surface which is opposed to the outer surrounding wall surface in radial directions and which confines an accommodating space to accommodate a seat post via insertion therein from the upper surrounding edge, and a slit which extends downwardly from the upper surrounding edge towards the lower surrounding member. The outer surrounding wall surface includes right and left lateral edge portions which are spaced apart from each other in a transverse direction relative to the axial direction to define the slit. A plurality of protuberances are disposed on the inner surrounding wall surface, and are angularly displaced from each other. Each protuberance projects radially and inwardly of the inner surrounding wall surface so as to abut against the seat post when the seat post is received in the accommodating space. Right and left jaw members are respectively attached on the right and left lateral edge portions, and are movable toward each other in the transverse direction to narrow the slit so as to bring the protuberances to abut against the seat post. A tightening member is disposed to releasably move the right and left jaw members toward each other in the transverse direction.